A chain joint is a mechanical apparatus which is capable of connecting two structures (generally two shafts) while allowing their mutual motion; such movement can be rotating or oscillating.
“Flexible chain joints” are used to connect two transmission shafts in mutual axial alignment, and they are capable of absorbing any misalignment owing to an imperfect mounting and to the inherent irregularities of the rotation.
The loss of power absorbed by the chain joint is minimal, so much so that it can be considered negligible.
These joints do not replace universal joints and they are not designed to absorb angular or axial misalignments, but only the vibrations and plays that are generated during the rotation of two shafts which are coupled axially.
Maintenance and mounting are extremely simple and rapid.
The joint is composed of a pin connected to the first structure (substantially a first link of the chain) and of a bushing connected to the second structure (substantially a link of the chain).
The contact surfaces between the pin and the bushing transmit the mechanical load from one structure to the other (i.e. they couple the links rigidly).
When the joint is subjected to a load, the pin tends to bend, resulting in a concentration of the load on contact surfaces of reduced size (the load will substantially be applied on edges).
Reducing the contact surface (and therefore localizing the load) results in an increase in the wear of the parts affected, with consequent rapid degradation of the joint.
This condition determines the necessity of overdimensioning the joints (in particular the pins) in order to make the desired performance levels possible, while minimizing wear.
Alternatively, the joint can be used at lower speeds than the design speeds in all cases in which a load greater than a preset threshold value could be applied to the pin.
In any case, the worst risk that can be encountered in conventional joints is a stoppage caused by the breakage or wearing-out of the pin.
The prior art documents U.S. Pat. Nos. 6,485,116 and 6,846,051 by Caterpillar Inc. disclose technical solutions aimed at overcoming the above mentioned problems.
These solutions involve the adoption of special contoured bushings that minimize the phenomenon of wear, thanks to a better distribution of the loads.
Against this, these implementation solutions require the adoption of bushings that are complex to make: since these are components which are present in great numbers in the joint, such complexity of manufacture translates to a high overall cost of the end product.